The present invention relates to a camera and more particularly, a camera with an auto program zoom control.
A camera with an auto program zoom (abbreviated to APZ) control is well known and widely appreciated. The APZ control comprises the steps of measuring an object distance D, systematically calculating a rate of zooming magnification from a program line representing the relation between object distance D and magnification .beta., calculating a focal length f from the formula, f (focal distance)=.beta..times.D and activating a zooming motor for setting the focal length of a zoom lens unit to the calculated value f.
Also, an auto power-off (abbreviated to APO) control is successfully employed so that when a given time has passed after the manipulation of switches and control means was ceased with a main power switch remaining turned on, unnecessary functions such as information on a display panel are deenergized for the purpose of energy saving. The APZ control allows the zooming action to be controlled by f=.beta..times.D, where D is the object distance and .beta. is the zooming magnification, for setting the focal length to f. Even if the object distance D remains unchanged for a given time, both the measurement of the object distance and the calculation of the focal length are carried out.
It is however understood that when no shutter release action is executed after the framing is fixed through the APZ control by an operator of the camera, both the measurement of the object distance and the calculation of the focal length become unnecessary. In addition, the action for such measurement and calculation is no more needed when the camera is not in use, for example, when installed in a camera case, with the switch for APZ control remaining turned on and will lead to unwanted energy consumption.
A technique of so-called intermittent charging is also known in which charging to an electronic flash unit built in the camera is conducted at equal intervals of a given time. As understood, if the charging of the flash unit remains incompleted, a shutter release action cannot be performed. While a known uncharge locking action is introduced, a chance for releasing the shutter will be lost.
A camera with an eye sensing control is also provided which can automatically be energized when its viewfinder is used by the camera operator. For example, disclosed in Japanese Patent Laid-open Publication 64-42639 (1989) is a camera which has a viewfinder provided with a light emitting diode and a light receiving diode so that when the viewfinder is peeped, the reflection of a light emitted from the light emitting diode is detected by the light receiving diode and thus, the driving of an auto focus lens unit starts. However, such a prior art camera allows the detection of a reflected light to be executed only once and erroneous detection caused by the effects of noise signals may be involved.